MPH programs' averages are somewhat lower than those for MDs. If I'm not mistaken, a 3.4/1200 is typical for an "elite" program.
Examples:
Columbia University Mailman School of Public Health:
Average GRE (Q): 671
Average GRE (V): 581
Average GPA: 3.4
University of Minnesota School of Public Health - Epidemiology MPH:
Average GRE (Q): 694
Average GRE (V): 561
Average GPA: 3.44
University of Minnesota School of Public Health - Maternal and Child Health MPH:
Average GRE (Q): 619
Average GRE (V): 522
Average GPA: 3.33